During surgical procedures, an incision is made to provide a surgeon with access to a patient's internal organs. At the end of the surgical procedure, the incision is closed to the external environment, thereby allowing the patient to heal and recover from the surgery. For surgical procedures to organs within a patient's thoracic cage, such as the heart and lungs, the patient's sternum may need to be separated to provide the surgeon with access to the organs.
The sternum is an elongated, generally flat, bone located longitudinally in the center of the thorax. The sternum has a composite bone structure with a dense outer shell formed from cortical bone surrounding a low density core formed from cancellous bone. The sides of the sternum are connected to rib bones through cartilage to form the anterior section of the thoracic cage, which protects the lungs, heart and other organs from physical trauma.
A sternotomy is a surgical procedure in which a midline longitudinal incision is made through at least a portion of the sternum to allow the opposing portions to be separated to provide access to organs within the thoracic cage. The sternotomy may be median, whereby the midline incision is made over the entire longitudinal length of the sternum. Alternatively, the sternotomy may be a less invasive partial sternotomy or hemi sternotomy, whereby the midline longitudinal incision is made over only a portion of the length of the sternum along with one or more transverse incisions from a peripheral edge of the sternum to the midline incision, which allow a relatively small portion of the sternum to be separated. When the surgical procedure is complete, the separated opposing portions of the sternum are approximated to one another to close the incision and secured to one another so that the incision may heal.
Conventional closure devices for approximating and closing sternal incisions include wires, cables or bands that generally wrap around the sternum between the ribs to provide a compressive load across the sternal incision. While these conventional devices restrain the sternum portions from pulling apart, they do little to resist other forms of relative motion, for example, sliding of one cut surface relative to the other or flexing motion about the incision. These non-prevented relative movements may result in pain and discomfort for the patient, as well as more severe complications such as infections, all of which may lead to prolonged medication, decreased lung capacity and a longer return to normal functionality (e.g. a return to work). Additionally, the relative movement may cause soft fibrous scar tissue to form across the incision, rather than the desired bone growth. The fibrous scar tissue must be subsequently removed with further surgical procedures.
Relative motion between the two sternal portions may also cause the conventional devices to loosen. For example, in the case of devices secured by twisted wire, the wire may untwist. More severely, the relative motion may cause the conventional devices to cut into and pull through the sternum bone, which also results in a loosening of the devices and separation of the sternal portions. This separation may delay healing or may result in additional surgical procedures to tighten or replace the conventional closure devices. The loosening or pulling through of the conventional devices may be caused by loading that the patient cannot practically control, such as cyclic loading due to normal respiration as well as less frequent high cycle loads generated during coughing or sneezing.
Another conventional closure device includes a metal plate that is fastened to an anterior surface of the sternum. While the metal plate inhibits relative movement between the two sternal portions better than conventional wires and cables, the metal plate has its own limitations and disadvantages. For instance, the thickness of metal plate closure devices results in discomfort to the patient. Additionally, the relative movement between the sternal portions may result in a failed screw purchase. With a failed screw purchase, one or more of the screws fastening the metal plate to the sternum strips the sternum bone, allowing the screw or screws to pull out of the bone. The loose screw or screws allow the metal plate to loosen from the sternum causing pain and discomfort for the patient. Furthermore, metal plate closure devices are costly and difficult to remove in the event there is a need for future access to the thoracic cavity.
Accordingly, there is a need for an improved method for sternal closure that overcomes the deficiencies of the prior art.